An electrophoretic device (20, 40, 50, is disclosed which is fabricated in a silicon wafer with many microscopic trenches (24, 44, 54) on its surface. The trenches are preferably covered by a cover (26, 46) so that the trenches can hold an electrolyte and an electrophoretic sample. Control circuits can be conveniently fabricated on the wafer as well. The control circuit is then used for applying electric fields to the trenches in an electophoretic process to separate the sample into its components. An electrophoretic method is also disclosed which is applicable to a device with a source and a sink electrode and at least a third electrode in or adjacent to the source. The third electrode is arranged transverse to the direction for applying voltages to the source and sink.; Voltages are applied to the electrodes so that the third electrode is at a higher or lower potential than the source and sink electrodes to attract charged sample components to their vicinity. Subsequently a different set of voltages is applied to the electrodes so that the sample components in the vicinity of the third electrode move towards the sink.